1) Field of the Invention
This invention relates to the manufacturing methods of high purity maltose and its reduced product.
2) Description of the Related Art
Maltose, 4-[.alpha.-D-glucopyranosyl]-D-glucose has been known as the main component of maltose starch syrup and used for a variety of foods because of its rich flavor.
On the other hand, maltitol, 4-[.alpha.-D-glucopyranosyl]-D-glutitol, the reduced product of the maltose, has found a variety of applications including foods, cosmetics, and medicines as it is less fermentable by the microorganisms and it contains sweet taste that is similar to sugar.
So far, it was harder to obtain high purity maltose or maltitol than to obtain high purity products of other saccharides. However, the attempts have been made to alleviate it by adopting specific saccharification method or by adopting the chromatographic separation method that has been used to improve the purity of other saccharides, to the manufacturing process of maltose or maltitol.
Among the many attempts to obtain high purity maltose or maltitol, the following are the typical cases:
(a) A method, as shown in Japanese TOKKYO-KOKAI-KOHO (18-month Publication of Unexamined Patent Application) SHOWA 57(1982)-134498 (hereinafter referred to as TOKKAISHO 57-134498), to obtain a high maltose liquid by acting .beta.-amylase and isoamylase after liquefying starch to low DE (dexitrose equivalent) with .alpha.-amylase.
(b) A method, as shown in Japanese TOKKAISHO 57-209000, TOKKAISHO 58-23799, TOKKAISHO 60-67000, TOKKAISHO 62-19210, to manufacture high purity maltose containing, for instance, not less than 93% of maltose by performing a chromatographic separation for constituent of saccharified liquid that is chiefly composed of maltose with maltose purity of 75 through 85% (in this specification, "%" means "percentage by weight" per solid substance, unless otherwise stipulated) and contains less glucose with alkali metal strong acid cation exchange resin.
(c) A method, well-suited for manufacturing maltitol in the form of powder or crystal, as shown in Japanese TOKKYOKOKOKU-KOHO (Publication of Examined Patent Application for Opposition) SHOWA 57(1982)-3356 (hereinafter referred to as TOKKOSHO 57-3356), TOKKOSHO 56-28153, TOKKOSHO 56-28154, to prepare maltose to which hydrogen has not yet been added, by acting, enzyme and the like (maltotriose resolutive activation / maltose resolutive activation is 2.5 or more) during saccharification.
(d) A method to obtain high purity maltitol--other than the method by reducing the maltose obtained through the above-mentioned methods, and undergoing several processings such as purification, separation, and crystallization--, as shown in Japanese TOKKAISHO 61-180797, by 1) liquefying the starch milk with a concentration of 25 through 45%, 2) saccharifying under the specified saccharification conditions, 3) obtaining saccharified liquid with the maltose purity of not less than 50 through 80%, 4) adding hydrogen to it, 5) performing a chromatographic separation, 6) obtaining sugar-alcohol liquid with the maltitol purity of 87 through 97.5%, 7) concentrating, and then 8) crystallizing it.
However, there are many problems to be solved with the conventional methods, and are not satisfactory as methods to manufacture high purity maltose or maltitol on a commercial basis.
For example, in the above-mentioned method (a), it is necessary to suppress, in liquefying the starch, the DE as low as possible. To put it concretely, it is necessary to suppress the DE not more than 2, preferably, 0.5 through 1.0 so as to obtain high purity maltose or maltitol.
To satisfy this DE value and values during the following processings, it is necessary to limit the raw material starch to expensive underground starch (potato starch, etc.) and suppress the liquefication concentration not more than 20% which is the lower value than that used for the conventional manufacturing process for high-maltose.
As a result, this method requires a very large saccharification tank than that used for manufacturing high-maltose syrup or glucose syrup that are produced and distributed on a large scale. At the same time, it is necessary to concentrate a large amount of water, leading to a drawback of an increased concentration cost.
The above-mentioned method (b) is a method that allows to use inexpensive ground starch. The processing that is responsible for increasing the purity of maltose is a method to separate maltose from DP 3 or more (degree of polymerization), that is oligosaccharides of trisaccharide or more. In this method, however, it is extremely difficult to perform a separation because the molecular weight ratio of maltose and maltotriose is small and there is a small difference in the nature necessary for other separations.
For this reason, a separation column with a great deal of capacity is required. A great deal of elution water is needed for separation. Thus, it requires a lot of cencentration cost. These are the defects of this method. Furthermore, an entry of impurities such as glucose into maltose fraction, that takes place often because the separation is difficult, keeps us from obtaining high purity maltose.
The point of the above-mentioned method (c) is that enzyme (maltotriose resolutive activation / maltose resolutive activation is 2.5 or more) and the like are acted during the saccharification. However, the defect is that it is difficult to obtain the enzyme because specific enzyme is used during saccharification. Another defect is that maltitol has to be produced from high purity maltose saccharification liquid obtained through saccharification by stopping the liquefaction at the level of around DE 1, because the increased glucose (because maltose is decomposed) keeps the yield of maltose at a low level.
In the above-mentioned method (d), the liquid used for separation is a mixture of sorbitol, maltitol, and sugar-alcohol of DP 3 or more. To take out a separation chiefly composed of maltitol, eight-column chromatographic separation unit has be operated in an extremely complicated manner.
Nonetheless, the separation status of each saccharic component is poor. Consequently, about 8% of maltotriitol can be seen in a fraction chiefly composed of maltitol.
The drawback of this method is that a contamination of sugar-alcohol of DP 3 or more checks the crystallization of maltitol, leading to a longer crystallization process and a lower yield of maltitol.
Because, moreover, the calcium type ion exchanger used for separation has a very strong adsorbing force against sorbitol, its elution is extremely slow as compared with maltitol or sugar-alcohol of DP 3 or more. As a result, chromatographic separation requires elution water five times the amount of raw material saccharification water. This means it is necessary to concentrate and remove a large amount of water, which is extremely inconvenient matter when viewed commercially.
Hence, a method for manufacturing high purity maltose and its reduced product which can solve the above-mentioned problems has been required.